Norovirus, also known as the stomach bug or the stomach flu, is a highly contagious intestinal virus. According to Dr. Peter Hotez, co-director of the Texas Children’s Hospital Center for Vaccine Development and dean of the National School of Tropical Medicine at Baylor College of Medicine, symptoms start as nausea and vomiting but may include diarrhea, too.
“For some reason, cruise ships and their buffets tend to be common sources of it,” Hotez said. “All it needs to do is get into one of the buffet foods, and then everyone’s eating it, and it can quickly spread.”
“It usually can produce explosive outbreaks where people get sick quickly. It has an onset within a day,” he added. “The good news is they’re self-limited illnesses, and within a few days, you’re fine.”
Norovirus, particularly between 2008 and 2014, according to data from the U.S. Centers For Disease Control and Prevention, was a common cause of gastroenteritis outbreaks on these vessels.
However, Hotez noted the recent incident of 25 passengers who embarked on a cruise and then reported symptoms while on a flight back from Vancouver to Houston was slightly unusual.
“Everybody was starting to get sick around the same time and boarded the plane around the same time,” he noted. “It could be really problematic if everyone is throwing up on an airplane at the same time, given the limited bathroom amenities. So, I could imagine quite a scene.”
The plane’s environment could also have increased the number of potential secondary infections. Despite norovirus typically spreading through contact with food, it can persist on surfaces.
In an emailed statement to the Houston Press, United Airlines mentioned actively coordinating with health authorities to address the situation. As a precautionary measure, the aircraft — a Boeing 737 MAX 8 — was taken out of service and is going through deep cleaning before operating again.
The flight that arrived in Houston last week had 163 passengers and six crew members. When it landed, at least one person on board said the pilot notified those inside the aircraft that the CDC had quarantined them. The Houston Fire Department was on the scene and evacuated three passengers, treating them on-site.
Hotez said outbreaks like this happen every year. The CDC’s Vessel Sanitation Program usually reports at least several outbreaks. The program helps investigate gastrointestinal illnesses on national and international cruise ships.
Through its reporting, the CDC does make clear that cases of norovirus that occur at sea are more commonly reported than those on land. This is because tracking the gastrointestinal virus and other illnesses on cruise ships is required.
According to data from the Cruise Lines International Association, cruise ship passengers have about a 1 in 5,500 risk of getting norovirus. Since the start of 2024, seven cruise ship lines have reported outbreaks of gastrointestinal illnesses. Of these, all but one was caused by norovirus.
One outbreak, detected on the Celebrity Summit, a cruise hosted by Celebrity Cruises®, was caused by the gastrointestinal virus, and its timeline corresponds with the arrival date of the Houston flight. However, officials have not identified the cruise line the passengers were on.
Hotez noted that the best ways for those wanting to go on a cruise or who are already on board to avoid contracting norovirus are to scrub down surfaces with hand wipes, wash their hands as much as possible and try to ensure certain food is protected.
“It’s really up to the cruise ships to make certain that none of the food handlers are sick. That’s really important. It’s also important that all food is relatively fresh,” he said. “If they have sick passengers, they need to quarantine them or keep them from spreading the virus around.”
Hotez added that cruise ships are not the only problem, as contaminated food, water and surfaces are the main sources of outbreaks. Close contact with individuals who are already infected can also lead to contracting norovirus.
In an email to the Houston Press, spokesman Nicholas Spinelli said public health officers from the CDC’s Houston Port Health Station worked with emergency medical services to evaluate ill passengers on board. Most of those who were sick reported mild gastrointestinal symptoms. None had a fever during the flight or upon assessment at landing.
Spinelli wrote that no passengers met CDC criteria for further public health follow-up. The CDC and other health authorities have not confirmed if those sick were infected with norovirus or another gastrointestinal virus or disease.
